Abstract

Micro-total analysis systems (æTAS) have enabled the miniaturization and simplification of environmental contaminant detection methods. Reduced reagent and sample consumption, speed of analysis, and field portability are only a few of the advantages æTAS systems provide. Centrifugal microfluidics have the added advantages of using centrifugal force for moving liquids, thereby avoiding solvent and filtration problems encountered with the electroosmotic flow typically used in æTAS manifolds. These properties suggest that centrifugal æTAS systems may offer many advantages as analysis platforms for the on-site analyses of a variety of important environmental pollutants. A model instrument has been developed and characterized for rapid, classical spectrochemical reactions. The system is designed for the determination of nitrite, nitrate and hexavalent chromium, three common pollutants. The system uses a single disc that requires 100æl of sample per analyte using a centrifugal disc that filters the water sample which is then mixed with the appropriate reagents in one or two steps using capillary valves, and is detected on-disc with a pathlength of 1.04 mm. Using a multi-wavelength technique for the precise determination of the reference signal, the detection limits for these three systems are 0.008, 0.6, and 0.03 mg*L -1 for NO 2 - -N, NO 3 - -N, and Cr 6+ respectively. A comparison between this technique and several conventional techniques highlights the strengths and limitations of the system.